"Implicit Skinning" Real-Time Skin Deformation with Contact Modeling

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  05 May 2013
"Implicit Skinning" Real-Time Skin Deformation with Contact Modeling

http://vimeo.com/65966757
http://irit.fr/~Rodolphe.Vaillant/?e=31




Quote: Paper abstract: Geometric skinning techniques, such as smooth blending or dual-quaternions, are very popular in the industry for their high performances, but fail to mimic realistic deformations. Other methods make use of physical simulation or control volume to better capture the skin behavior, yet they cannot deliver real-time feedback. In this paper, we present the first purely geometric method handling skin contact effects and muscular bulges in real-time. The insight is to exploit the advanced composition mechanism of volumetric, implicit representations for correcting the results of geometric skinning techniques. The mesh is first approximated by a set of implicit surfaces. At each animation step, these surfaces are combined in real-time and used to adjust the position of mesh vertices, starting from their smooth skinning position. This deformation step is done without any loss of detail and seamlessly handles contacts between skin parts. As it acts as a post-process, our method fits well into the standard animation pipeline. Moreover, it requires no intensive computation step such as collision detection, and therefore provides real-time performances.

This is the future standard of skinning in DCC soft !

Autodesk should hire them !
 
  05 May 2013
Great video. Love seeing people working on deformation solutions. Deformations are the biggest bottle neck in character setup and we need all the solutions we can get.

It's why I'm considering moving to Modo. There deformation options seem to be the most advanced.
 
  05 May 2013
If you mean that they are the biggest bottleneck in terms of rig performance, that couldn't be further from the truth.

To the degree of visualization required by animators deformations are never the bottleneck to performance, and they are getting faster by the day. The graph for the increasingly complex and incresingly common uberrigs are always the bottleneck, as they cripple FPS by their latent nature.

It's a great paper and a great idea, but given that performance level is for the transforms + deformations alone it'd be more suitable for a deformation rig, for a high qualtity flipbook level, because with the added cost of the control rig it'd drop considerably below the real time threshold.

One of the things that makes it great is that it rides the back of a DQ skin, which means it'd be trivial to turn on/off just for flipping the shot.

It's basically an elegant, stateless de-intersection system more so than it's what one would consider skinning in a more traditional sense.
Similar solutions (reprojection and smoothing) have been common for a while in many places. The novel take they have on it is that of field functions and global field composition, which is a tremendous help in de-intersecting which through more traditional methods would require a second mesh and double the skinning work, while they replace that step with an elegant pre-comp pass.
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  05 May 2013
Originally Posted by ThE_JacO: If you mean that they are the biggest bottleneck in terms of rig performance, that couldn't be further from the truth.

To the degree of visualization required by animators deformations are never the bottleneck to performance, and they are getting faster by the day. The graph for the increasingly complex and incresingly common uberrigs are always the bottleneck, as they cripple FPS by their latent nature.

It's a great paper and a great idea, but given that performance level is for the transforms + deformations alone it'd be more suitable for a deformation rig, for a high qualtity flipbook level, because with the added cost of the control rig it'd drop considerably below the real time threshold.

One of the things that makes it great is that it rides the back of a DQ skin, which means it'd be trivial to turn on/off just for flipping the shot.

It's basically an elegant, stateless de-intersection system more so than it's what one would consider skinning in a more traditional sense.
Similar solutions (reprojection and smoothing) have been common for a while in many places. The novel take they have on it is that of field functions and global field composition, which is a tremendous help in de-intersecting which through more traditional methods would require a second mesh and double the skinning work, while they replace that step with an elegant pre-comp pass.


Yes sorry not performance bottlenecks but creation bottlenecks.

So in other words the time it takes to rig a character 70% or more is spent on deformations, Because the standard tools are almost useless.

Painting weights with normalization is a joke. The first and last thing that needs to be considered when building a rig is deformations, and without efficient tools it's a very tedious and Time-consuming job.

Reading the book "art of moving points "and looking at Modo gives me hope though.
 
  05 May 2013
Well, this looks really promising - not sure if/when this type of skinning will show up in the standard packages but I'm looking forward to it. The sort of deformation side effects shown in the video are things it seems we've been dealing with for 15 years, it will be nice not to have to think about penetrating surfaces and bulging joints as much. I really do think the biggest pipeline gains to be had right now are in the rigging, skinning, and animation processes.

-Greg
 
  05 May 2013
Originally Posted by gauranga108: Yes sorry not performance bottlenecks but creation bottlenecks.

So in other words the time it takes to rig a character 70% or more is spent on deformations, Because the standard tools are almost useless.

Painting weights with normalization is a joke. The first and last thing that needs to be considered when building a rig is deformations, and without efficient tools it's a very tedious and Time-consuming job.

Reading the book "art of moving points "and looking at Modo gives me hope though.

Bear in mind this will not cut into painting weights, the fields are derived from the bindings, and there's a skinning step before this method can run it de-intersection like pass of reprojection and smoothing.
If this cuts into anything it's into eventual PSD/shapeFix modelling that some people do afterwards, that's what it takes care of.

It's also debatable whether deformations take the longest.

At a certain level, and at a certain amount of repetition (IE: same rig gets fit to many different creatures that all need their skinning), maybe, but at work, for us, the full skinning and binding with the first de-intersection step (where using this would get us) usually only takes a day or two, which is nothing compared to the time it takes for a fresh control rig from scratch, or even a re-conforming of existing components to new requests or a new anim supe with requests differing from the previous one.

Good painting and binding tools are necessary for that though, and if you're using OOTB Maya no wonders you think it an unnecessarily long process
This adds to that though, not take away from it, it's not an automatic binding solution.
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  05 May 2013
There's been a lack of innovation in the skinning department compared to other areas in cg, so I find papers like this one always interesting.

This solution looks much better than what we have available at the moment, though I would have hoped to see some shoulder deformation examples in those vids too.

Another thing I was hoping to see by now in our industry was a muscled mannequin for bipeds and quadropeds so you could transform and scale that mannequinn shape to fit your geometry and the muscles would drive the skin, skin sliding bulging etc...
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  05 May 2013
Quote: Good painting and binding tools are necessary for that though, and if you're using OOTB Maya no wonders you think it an unnecessarily long process


OOTB?

thanks
 
  05 May 2013
Originally Posted by mustique: There's been a lack of innovation in the skinning department compared to other areas in cg, so I find papers like this one always interesting.


All the big studios have robust muscle systems by now so they don't care. The rest of us stuck between small and big are unlucky. But we do represent a huge market for 3rd parties IMHO.
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  05 May 2013
Originally Posted by gauranga108: OOTB?

thanks

"Out Of The Box" - plain vanilla install with no third party plugins
 
  05 May 2013
Originally Posted by Laa-Yosh: All the big studios have robust muscle systems by now so they don't care. The rest of us stuck between small and big are unlucky. But we do represent a huge market for 3rd parties IMHO.

You might be surprised at how not robust many muscle systems are, and how resource intensive to set up they can be.
You also can't always use it for every creature.
They also tend to be used for reasons other than what the paper addresses, which is more PSD territory, and PSD is very labour intensive, and I'm personally not a huge fan of it.

This is actually a damn good paper, the approach to addressing reprojection is both ingenous and clever, and it has applications for the pre-skin pass used in many high-end muscle systems, not to mention it's brilliant for non muscled setups.
It's also more honestly presented than a lot of similar material.

I know it got me and a few other people looking into it for sure.
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  05 May 2013
Originally Posted by ThE_JacO: You might be surprised at how not robust many muscle systems are, and how resource intensive to set up they can be.
You also can't always use it for every creature.
They also tend to be used for reasons other than what the paper addresses, which is more PSD territory, and PSD is very labour intensive, and I'm personally not a huge fan of it.

This is actually a damn good paper, the approach to addressing reprojection is both ingenous and clever, and it has applications for the pre-skin pass used in many high-end muscle systems, not to mention it's brilliant for non muscled setups.
It's also more honestly presented than a lot of similar material.

I know it got me and a few other people looking into it for sure.


Weta's Tissue system looked very cool when FXGuide featured it, but they obviously weren't giving a public run-down all the problems they encountered. It did seem like as close to an all-purpose solution that I've seen, and using it as a shortcut to baking PSD's simplified the process a lot.

I haven't worked with much Mo Cap animation, only one hyper-real project, but one thing that's always struck me is that the pivots on for joints are always slightly offset, since they have to be on the surface rather than the centre of a joint. Doesn't this always introduce minor offsets that have to be countered? For me its more of a hypothetical question but its something thats interested me for a while.
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  05 May 2013
[QUOTE=
I haven't worked with much Mo Cap animation, only one hyper-real project, but one thing that's always struck me is that the pivots on for joints are always slightly offset, since they have to be on the surface rather than the centre of a joint. Doesn't this always introduce minor offsets that have to be countered? For me its more of a hypothetical question but its something thats interested me for a while.[/QUOTE]

that's something that I've been wondering myself for ages!
 
  05 May 2013
We do, when it makes sense, rig for separating and buffering joints, and often enough controls are added to add a certain amount of give in certain areas for animators to propagate extensions or recoil in layers (IE: femur and humerus actually have a fair bit of give in them to part them from their socket and can push against the tissues).

Some times it's at a deformation level, derived from the control rig into the deformation rig, some other times where it has an impact on the motion it might be factored directly into the control rig, especially if there's enough play that it'd affect arcs.
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  05 May 2013
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